Apparatus for producing composite wooden boards and the like



Jan. 3, 1956 E. BEHR APPARATUS FOR PRODUCING COMPOSITE WOODEN BOARDS ANDTHE LIKE Filed Jan. 3, 1951 INVENTOR.

Erwin Be h r ATTORNEY United States Patent M APPARATUS FOR PRODUCINGCOMPOSITE WOODEN BOARDS AND THE LIKE Erwin Behr, Wendiingen (Neckar),Wurttemberg, Germany, assignor to Allwood Incorporated, Glarus,Switzerland, a corporation of Switzerland My invention relates toapparatus for producing wood composition boards and the like productsconsisting essentially of wood chips or shavings.

Wood composition products have been made from short-fibered chips byagglomeration With a binder and compression. As a rule, chips resultingas waste from the planing or sawing of wood were used; and to obtain acomparatively uniform product, the larger chips were cut up intoshort-fibered particles. Obviously this treatment amounts to adestruction of the wood whereby the mechanical resistivity particular towood fibers stressed in the longitudinal direction is lost. Thedestruction of this resistivity also requires considerable mechanicalforce.

For converting such a short-fibered material into boards, it is usuallymixed with water which must subsequently be eliminated by drying. Tosecure a firm coherence of the short-fibered particles, high pressure isused. Hence, a considerable consumption of wood is needed to produce acomparatively thin sheet or board. Nevertheless, and despite thecomparatively large amount of admixed binder, the strength of a woodenbody produced in this manneris rather low and renders these productsunsuitable for the production of furniture and g the like. i

It is an object of my invention to provide fabricating apparatussuitable for mass production of wood composition boards or the likeproducts that combine low manufacturing cost with improved mechanicalstrength.

To this end, and in accordance with my invention, I provide a mixing andcompressing extrusion apparatus for converting elongated andlongitudinally fibered wood particles together with a binding agent intoa precompressed sheet of material of substantially uniform thickness.The essential features of the apparatus described below will be betterunderstood if first the particular character of the wood particle massto be fabricated is taken into account.

The raw material to be used for the purpose of the invention consists oflong fine chips or shavings which form narrow fiber bundlessubstantially spread straight in the longitudinal direction of thefibers and which measure in length at least about the twentyfold, and asa rule a much greater multiple, of their Width, while being very thinand measuring not more than about 1 mm. and preferably 0.3-0.5 mm. inthickness. These fiber bundles are obtained by cutting wood insucli amanner as to preserve as far as possible its natural longitudinal fiberstructure. The long-fibered particles are so distributed in the productto be made that the fibers extend in every direction, longitudinally aswell as laterally and through all three dimensions, thus imparting greatstrength and resistivity to the finished product.

Due to their very small width, amouning to only a few millimetersmaximum, these fiber bundles undergo practically no swelling orshrinking so that the structural bodies such as sheets, plates orboards, are highly resistant to the action of moisture.

Patented Jan. 3, 1956 The long-fibered particles are mixed with asuitable binder, either by themselves or with the addition ofshortfibered particles or smalllaminae, or together with uniformlysubdivided chips which serve to fill any cavities. The mixture is thenformed to the desired shape by pressure. It is neither necessary nordesirable that the Wood fibers be completely impregnated with thebinder, but suffices if they are wetted on their surfaces with anagglutinant dissolved in water. Not more than about 20 percent of thesolid agglutinant are then contained in'the mixture before it iscompressed, while in the compressed product the solid binder is presentin a proportion not exceeding 7.5 percent. A synthetic water-solubleglue is particularly suitable.

The particles thus prepared are mixed, in dry or moist condition, insuch manner that fibers extend in practically all directions and areintimately felted with each other. The mass consisting of felted fibersand a binder is then shaped under pressure to form the desired product.

The apparatus according to the invention serves to perform and improvean essential portion of the abovedescribed fabricating process, namelyto pre-compress and shape the wood particle mixture into flat sheetsprior to subjecting them to the final pressing operation in conventionalpresses. The apparatus has a feed hopper for receiving the particlemixture mounted on top of a downwardly tapering housing whichcommunicates at its bottom with an outlet conduit which is elongated inthe feed direction and has along its length a fiat cross section. Forcedfeed means, particularly studded rollers, are provided to feed theparticle material through the housing and extruding it through the flatconduit, whereby the material is precompressed as it passes through thetapering housing and is molded into a sheet of substantially uniformcross section as it is extruded from the conduit. The resulting coherentsheet is then ready for final pressing.

An embodiment of apparatus according to the invention is showndiagrammatically in Fig. 1 of the drawing in a vertical sectional view,and Fig. 2 shows another embodiment of said apparatus also in verticalsection.

The apparatus shown in Fig. 1 has a housing 7 Whose cross sectiondecreases gradually in the downward direction. A hopper 18 mounted onthe top of the housing serves to provide a continuous supply ofwood-particle material. Several rollers 8, 9a, 9b, 9c are revolvable inthe housing. When in operation, the top roller 8 revolves clockwise sothat the portion of its periphery close to the housing wall moves in thefeed direction of the descending particle material, while the otherperiphery portion moves in opposition to that direction. The rollers 9a,9b, 9c revolve counter-clockwise. All have studs or ribs 10 mounted ontheir circumferences.

The fiber bundles 1, which may be mixed with other matter, areintroduced through hopper 18, and then gripped by the top roller 8. Someof the material is forced through the channel between the top roller andthe housing wall. Thence the material comes into contact with the otherrollers which mix it intimately and forces it gradually downward throughthe narrowing housing space thus compressing the particles until theyenter into a flat horizontal conduit 11. The conduit is sufiicientlylong in the feed direction to extrude the particle mass as a feltedribbon or sheet of sufiicient coherence to permit being withdrawn andintroduced into the final shaping press.

In the apparatus of Fig. 2, two opposite walls of the housing are formedby conveyor belts 12, 13 running at controlled speed. Their top drums14, 15 are spaced farther from each other than their bottom drums 16,17. The conveyor belts secure the downward flow of the fiber material.The fiber bundles 1 are fed through the hopper 18 along a studded roller19 which vibrates in the axial direction and grips and mixes thebundles. The fiber material is gradually lowered, mixed and compresseduntil it enters a horizontal conduit 11 leading to the shaping press.Felting of the fibers can be improved by adjusting the relative positionof the Walls of'the housing formed by the conveyors 12, 13.

It willbe obvious to those skilled in the art upon a studyof thisdisclosure that my invention permits of various modifications and may beembodied in apparatus involving details other than those herespecifically shown and described, without departing from the essentialfeatures of my invention and within the scope of the claims annexedhereto.

I claim:

'1. Apparatus for producing wood composition products from long-fiberedwood particles, comprising a hopper for supplying a mass of particles, ahousing disposed below said hopper and communicating therewith, saidhousing having a bottom opening and being gradually tapering fromsaidhopper to said Opening, an outlet conduit of horizontally fiat shapeadjoining said bottom opening for extruding a tare-compressed she'et'ofparticles, and a number of studded revolvable rollers disposed withinsaid housing above one another for's'equem tially forcing the particlesfrom said hopper to said conduit, the uppermost one of said rollershaving a direction of revolution opposite to that of the other rollers.

2. Apparatus for producing Wood composition products from long-fiberedwood particles, comprising a hopper for supplying a mass of particles, avertically elongated housing adjacent and below said hopper, saidhousing having a bottom opening and being gradually tapering from saidhopper to said opening, a substantially horizontal outlet conduit ofhorizontally fiat shape adjoining said opening for extruding apro-compressed sheet of particles, and a number of studded mixingrollers revolvably disposed in said housing above one another along sideone of the vertical housing walls and having a downwardly decreasingspacing respectively from the opposite housing wall, a majority of saidrollers having at the side of said opposite housing wall a downward 4direction of revolution for feeding the particles through said housingand. conduit.

3. Apparatus for producing wood composition products from long-fiberedwood particles, comprising a hopper for supplying a mass of particles, avertically elongated housing disposed adjacent and below said hopper andhaving two substantially vertical side walls opposite each other, saidhousing having a bottom opening and being gradually tapering from saidhopper to said opening, an outlet conduit of horizontally flat shapeadjoining said opening for extruding a pre-compressed sheet ofparticles, and a number of studded rollers above one another along oneof said vertical walls of said housing, an upper one of said rollershaving on the side'of said other vertical wall an upward direction ofrevolution, and a majority of said rollers including the lowermostroller having on said other wall side a downward direction ofrevolution.

References Cited in the file of this patent UNITED STATES PATENTS565,291 Meyers Aug. 4, 1896 618,916 Stewart Feb. 7, 1899 845,329Bottomley Feb. 26, 1907 1,006,452 Anderson Oct. 24, 1911 1,321,576Wakeman Nov. 11, 1919 1,560,313 Pittman Nov. 3, 1925 1,599,253 SkolnikSept. 7, 1926 1,726,511 Henry et al Aug. 27, 1929 1,969,291 Antoni Aug.7, 1934 1,977,515 Klippel Oct. 16, 1934 2,004,936 Dorn et al June 18,1935 2,066,734 Loetscher Jan. 5, 1937 2,280,022 Banigan et a1 Apr. 14,1942 2,446,304 Roman Aug. 3 1948 FOREIGN PATENTS 386,027 Great BritainJan. 12, 1933 608,252 Great Britain Sept. 13, 1948 OTHER REFERENCES WoodFibers From Veneer Waste, by A. Elmendorf, Paper Trade JournaL Feb. 9,1950, pages 29-31.

